The present invention relates to a substrate processing method and a semiconductor device manufacturing method, and in particular to a substrate processing method and a semiconductor device manufacturing method that employ a proton injection process and a laser irradiation process.
In the case of a conventional white LED product, a blue light emitting diode GaN is made grow on the surface of an ultraprecision-processed sapphire substrate (alumina oxide) that is cheap and can easily cause epitaxial growth, and then an LED device is obtained by layering a white conversion device (such as Ce) on GaN in order to obtain white light. In the future, to lower the price of LED products, it is effective to use a technique of producing thin film of sapphire single crystal, which is then used as a substrate for GaN deposition.
Further, if a circuit could be formed on a semiconductor substrate of cheap sapphire by microfabrication process, then a masking process and a subsequent corrosion working process could be omitted. This will largely contribute to cost reduction in manufacturing a semiconductor device.
As a method of producing a thin film of sapphire, it might be possible to consider applying a method that carries out the smart cut process by injecting protons into Si semiconductor and applying heat to it (See Non-Patent Document 1 and Patent Document 1). Until now, however, there is no example that has applied this method to sapphire as an alumina oxide in order to carry out a thin film producing process and a microfabrication process. There are past reports of various tests of ion injection and laser irradiation of sapphire. The former, however, was carried out mainly for studying color centers generated by ion injection (See Non-Patent Documents 2-7), and the latter for studying damage due to laser irradiation (See Non-Patent Documents 8-10). There is no example that combines these techniques in order to carry out a microfabrication process and a thin film producing process for sapphire itself.
Patent Documents 2 and 3 disclose methods of preparing a nitride semiconductor substrate. In these methods, atomic bonds within a substrate are weakened by ion injection or the like, and nitride semiconductor is made grow on the substrate, and then the substrate and the nitride semiconductor are separated by laser irradiation.